Pytest fixture to change actors `restart_limit` doesn't work as expected

[leandro-lucarella-frequenz]

What happened?

Originally created by @ela-kotulska-frequenz

We added fixture to change the restart_limit in actors, but we didn't enable it for all actors in unit tests.

It looks like if we use this fixture, we can't pass any arguments to the tests functions.

Example:

https://github.com/frequenz-floss/frequenz-sdk-python/blob/20e1dffadcb728443190e1dcfae45d68545ba962/tests/configs/test_config_manager.py

If class TestActorConfigManager: derives after (IsolatedAsyncioTestCase) then the tests fails with error:

self = <tests.mos_framework.configs.test_config_manager.TestActorConfigManager testMethod=test_update>
func = <bound method TestActorConfigManager.test_update of <tests.mos_framework.configs.test_config_manager.TestActorConfigManager testMethod=test_update>>
args = (), kwargs = {}

    def _callMaybeAsync(self, func, /, *args, **kwargs):
        assert self._asyncioTestLoop is not None
>       ret = func(*args, **kwargs)
E       TypeError: test_update() missing 1 required positional argument: 'config_file'

What did you expect instead?

The restart_limit is overridden correctly.

Affected version(s)

All

Affected part(s)

Unit, integration and performance tests (part:tests)

Extra information

Fixture to change restart_limit:

frequenz-sdk-python/tests/conftest.py

Lines 18 to 31 in 20e1dff

	@pytest.fixture(scope="session", autouse=True)
	def disable_actor_auto_restart(): # type: ignore
	"""Disable auto-restart of actors while running tests.
	Since this is auto-use, the yield part (and restore of the variable) is not
	strictly needed, but we leave it as an example.
	Note: Test class must derive after unittest.IsolatedAsyncioTestCase.
	Otherwise this fixture won't run.
	"""
	original_restart_limit = decorator.BaseActor.restart_limit
	decorator.BaseActor.restart_limit = 0
	yield
	decorator.BaseActor.restart_limit = original_restart_limit

[leandro-lucarella-frequenz]

Comment by @jakub-toptal

Looks like the IsolatedAsyncioTestCase class doesn't properly pick up pytest fixtures. IsolatedAsyncioTestCase does expose some methods like setUp and tearDown so if we really needed, we should be able to create a fixture ourselves there instead of using pytest. The module you mentioned, doesn't need to inherit from IsolatedAsyncioTestCase, but if it did, we could move the logic for creating a tmp config file into setUp method, save it as an instance attribute, e.g. self.config_file, then use that in the test method, and finally clean it up in tearDown.